The present invention relates to an optical fiber cable which includes at least one optical fiber unit in which at least one coated optical fiber or optical fiber tape is accommodated in a groove formed on a rod-like spacer. More particularly, the present invention relates to the optical fiber cable which has a water running preventive function so as to prevent water from spreading in the cable interior when an outer sheath of the cable is damaged to allow water to enter thereinto. The present invention also relates to an optical fiber cable which includes at least one optical fiber unit. The unit includes a central rod-shape spacer, a plurality of optical fiber tapes accommodated in each of a plurality of grooves formed on an outer peripheral surface of the rodshaped spacer, and an outer support winding disposed over the spacer.
Throughout the specification and claims, the term "optical fiber tape" implies a tape in which a plurality of optical fibers are embedded in parallel to one another.
Generally, in the optical fiber cable, water or moisture may enter the cable interior if an outermost sheath of the cable is subjected to damage, and various disadvantages may occur such as degradation of optical fiber strength and degradation of transmission characteristic due to freezing. Therefore, conventionally, tapes, braids and particles formed of a material having water absorbing and swelling characteristics are embedded in spaces or gaps in the optical fiber cable in order to absorb water or moisture and to block the water.
According to the conventional water blockage type optical fiber cable which accommodates therein at least one optical fiber unit, there are large spaces in volume between the outer peripheral surface of the optical fiber unit and the outermost sheath member of the cable. Therefore, a large amount of water absorbing and swelling material is required in order to satisfactorily the space. However, since the material is expensive, the resultant water blockage type optical fiber cable also becomes expensive. Therefore, it is impractical for use in actual practice in light of production costs.